I've done my bit of research and wanted to come here before pulling the trigger. The current decision is the cd changer slot thing. I found this on ebay and it's similar to what many people have chosen to do:

Car CD MP3 Player Radio Interface Aux in Adapter for Lexus Toyota Camry Corolla | eBay

My question was, is there a cheaper method than this? I'm good at soldering, good with electronics and can follow instructions pretty well. If there's a way i can solder myself into this, or if there's a cheaper hookup method let me know.

Also, if the item I linked wont work, please let me know.

 

A generic way to add Aux for MP3/phone audio is to buy an FM modulator from WalMart for less than $25 and plug into cig. plug. I have one that will take an audio cable input, SD card or USB stick. Plays the files well and just have to tune FM radio to programmable channel, mine does all frequencies on radio band, just have to pick the most isolated frequency. Also can share tunes with friends when they tune into your "channel"!!
Other than that it would depend if your head unit has AUX input, don't know since you have no model year listed. The HU model is on the lower right corner of the faceplate.
Good luck, enjoy...